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| United States Patent |
6,262,311
|
|
Maassen
, et al.
|
July 17, 2001
|
Process for the preparation of 2,3,5-trimethyl-p-benzoquinone
Abstract
Process for the preparation of 2,3,5-trimethyl-p-benzoquinone by oxidizing
2,3,5-trimethylphenol or 2,3,6-trimethylphenol with oxygen or an
oxygen-containing gas mixture in the presence of a catalyst system which
can be a copper halide and a transition metal halide; for example iron,
chromium, manganese, cobalt, nickel, zinc or a rare earth halide, in a
two-phase reaction medium, at elevated temperature.
| Inventors:
|
Maassen; Ralf (Hanau, DE);
Krill; Steffen (Speyer, DE);
Jager; Barbara (Freigericht, DE);
Huthmacher; Klaus (Gelnhausen, DE)
|
| Assignee:
|
Degussa AG (Dusseldorf, DE)
|
| Appl. No.:
|
688185 |
| Filed:
|
October 16, 2000 |
Foreign Application Priority Data
| Oct 15, 1999[DE] | 199 49 795 |
| Current U.S. Class: |
568/358; 362/377 |
| Intern'l Class: |
C07C 045/00; C07C 049/105 |
| Field of Search: |
552/310
568/358,362,377
|
References Cited
U.S. Patent Documents
| 5041572 | Aug., 1991 | Jessel et al. | 552/310.
|
| 5104996 | Apr., 1992 | Hirose et al. | 552/310.
|
| Foreign Patent Documents |
| 0 294 584 | Dec., 1988 | EP.
| |
| 475272 | Mar., 1992 | EP.
| |
| 0 475 272 | Mar., 1992 | EP.
| |
| 54-98728 | Aug., 1979 | JP.
| |
| 5-97834 | Apr., 1993 | JP.
| |
| 9-202746 | Aug., 1997 | JP.
| |
Primary Examiner: Dees; Jose' G.
Assistant Examiner: Pryor; Alton
Attorney, Agent or Firm: Smith, Gambrell & Russell, LLP
Claims
What is claimed is:
1. A process for the preparation of 2,3,5-trimethyl-p-benzoquinone
comprising oxidizing trimethylphenol with oxygen or an oxygen-containing
gas mixture in the presence of a catalyst in a two-phase reaction medium
at a temperature of 20 to 120.degree. C., wherein the reaction medium
consists of water and an aliphatic alcohol having from 5 to 10 carbon
atoms or consists of water and an aliphatic alcohol having from 1 to 4
carbon atoms and an aromatic hydrocarbon, and wherein the catalyst
comprises a copper halide and additionally a transition metal halide
selected from the group consisting of iron, chromium, manganese, cobalt,
nickel, zinc and a halide of a rare earth element.
2. The process for the preparation of 2,3,5-trimethyl-p-benzoquinone
according to claim 1, wherein said reaction medium is water and a mixture
of an aliphatic alcohol having from 1 to 4 carbon atoms and toluene or
benzene.
3. The process for the preparation of 2,3,5-trimethyl-p-benzoquinone
according to claim 1, wherein said reaction medium is water and 1-hexanol,
1-heptanol, 2-ethylhexanol or 1-octanol.
4. The process for the preparation of 2,3,5-trimethyl-p-benzoquinone
according to claim 1, wherein chromium(III), manganese(II) or cobalt(II)
chloride is the transition metal halide.
5. The process for the preparation of 2,3,5-trimethyl-p-benzoquinone
according to claim 1, wherein cerium(III) chloride is the halide of a rare
earth element.
6. The process for the preparation of 2,3,5-trimethyl-p-benzoquinone
according to claim 1 further comprising bring an organic phase containing
said trimethylphenol into contact with an aqueous phase containing said
catalyst to produce a reaction mixture, bring said reaction mixture into
contact with said oxygen-containing gas mixture, and after completion of a
reaction to produce said benzoquinone, separating the organic phase from
the acqueous phase.
Description
INTRODUCTION AND BACKGROUND
The present invention relates to a novel process for the preparation of
2,3,5-trimethyl-p-benzoquinone by oxidizing phenols by means of oxygen in
the presence of a two-phase liquid reaction medium containing a catalyst
mixture of copper chloride and additionally a transition metal halide
selected from the group consisting of iron, chromium, manganese, cobalt,
nickel, zinc and a halide of a rare earth element. Both
2,3,5-trimethylphenol and 2,3,6-trimethylphenol may be used as reactants
in that process.
2,3,5-Trimethyl-p-benzoquinone is an intermediate which is used inter alia
in the preparation of .alpha.-tocopherols (vitamin E).
The oxidation of trimethylphenols to 2,3,5-trimethyl-p-benzoquinone is
known.
The use of inorganic oxidizing agents, including potassium permanganate,
manganese dioxide and lead oxide, has been described, it being necessary
in prior-known processes to use stoichiometric amounts of the oxidizing
agent. The use of stoichiometric amounts of those expensive oxidizing
agents causes high chemicals consumption and produces streams of waste
which are polluted with the corresponding reduced metals and must be
regenerated or disposed of at great expense.
Also known are catalytic processes in which the trimethylphenol oxidation
is carried out in the presence of a metal catalyst using an
oxygen-containing gas as the oxidizing agent. Conversion of those
processes for commercial application, for example using a cobalt-salene
complex catalyst, is complicated and expensive owing to the short life of
the catalyst, since the addition of not inconsiderable amounts of fresh
catalyst and the disposal or costly treatment of considerable amounts of
discharge stream polluted with metals are necessary.
In EP 0 659 727, for example, tetraaza[14]annulene which contains a
complex-bonded heavy metal ion is described as the oxygen-carrying
catalyst. That catalyst complex is destroyed during the oxidation and is
not recyclable, so that it is not suitable for commercial use.
In this connection, U.S. Pat. No. 3,796,732 describes the use of copper
chloride as the catalyst for the reaction, wherein the operation is
carried out in a homogeneous phase in the presence of an inert solvent
such as DMF and there arises the problem of recovery of the catalyst,
which can be solved technically only with a great expenditure.
In JP 17585/1978, an improvement in the yields is described using a
catalyst system consisting of copper ions and halogen ions. Disadvantages
of that process are that, in spite of good yields, the space-time yield is
low and it is necessary to extract the catalyst using large amounts of
water and to remove water in order to recycle the catalyst, and, not
least, that residual water has a negative effect on the catalyst
performance of the recycled catalyst.
In JP 93931/1975, halogens or halogenated compounds are added during the
recycling in order to maintain the catalyst activity, but those compounds
are used up rapidly under the reaction conditions and therefore must be
supplemented regularly. That is expensive in terms of process technology
and leads to markedly increased production costs.
A possible method of avoiding the problems of catalyst recycling while
simultaneously maintaining catalyst activity is described in RU-2 039 037,
in which the oxidation of trimethylphenol and structurally related
compounds in the presence of a heterogeneous catalyst by means of oxygen
or an oxygen-containing gas is disclosed.
A disadvantage of that process has proved to be the expensive preparation
of the heterogeneous catalyst, which is obtained by applying a monovalent
copper chloride in the presence of ammonium chloride and an alkali metal
chloride to aluminum hydroxide as support in the presence of a defined
amount of phosphoric acid.
According to EP 0 127 888, aqueous solutions of Li(CuCl.sub.3) in the
presence of a high excess of the corresponding lithium halide are used as
the oxidation catalyst. It has been found, however, that despite good
yields, conversion of that process for commercial application is not
advantageous because large excesses of expensive lithium halide must be
used, the complex copper(II) catalyst must be expensively prepared before
the reaction, and at least equivalent amounts of the catalyst, based on
trimethylphenol, must be used to achieve good yields.
EP 0 167 153 describes the use of an aqueous catalyst solution consisting
of Li(CuCl.sub.3) or corresponding copper(II) complexes in the presence of
an excess of the corresponding lithium halide.
In EP 0 294 584 there is also described a process for the preparation of
2,3,5-trimethyl-p-benzoquinone in the presence of a catalyst consisting of
copper(II) chloride and lithium chloride in a two-phase reaction medium
consisting of water and a mixture of an aromatic hydrocarbon and a lower
aliphatic alcohol having from 1 to 4 carbon atoms. The use of a complex
organic solvent mixture, which must be recovered by distillation following
the reaction, is not advantageous from a commercial point of view.
Another variant of the oxidation in a two-phase reaction system is
described in EP 0 369 824. The catalyst consists of a binary system
consisting of a copper(II) halide and a nitrogen-containing compound,
preferably a hydroxylamine, an oxime or an amine or the corresponding
ammonium salts. It has proved disadvantageous that the nitrogen-containing
catalyst component is decomposed under oxidative conditions, cannot be
recycled, and therefore gives rise to high costs.
EP 0 475 272 describes oxidation in the presence of an oxygen-containing
gas using a catalyst consisting of a copper(II) halide and an alkaline
earth metal halide in a two-phase solvent system consisting of water and a
saturated aliphatic alcohol having from 5 to 10 carbon atoms. In that
process, the active catalyst is formed in situ from the copper(II) salts
and the alkaline earth metal additives and the organic solvent system has
a sufficiently high flash point in comparison with the reaction
temperatures used. However, in order to achieve good conversions and
yields, the catalyst must be added in stoichiometric amounts.
The reaction in aliphatic alcohols having from 12 to 18 carbon atoms that
is described in EP 0 387 820 likewise permits oxidation at temperatures
below the flash point of the organic solvent, but the process is not very
attractive commercially since the reaction and the isolation of the
2,3,5-trimethyl-p-benzoquinone are very complicated owing to the
relatively high melting points and boiling points of the alcohols.
An object of the present invention is to provide a novel process for the
preparation of 2,3,5-trimethyl-benzoquinone in order to solve the, in some
cases, considerable disadvantages described in the prior art as regards
the cost of the materials used, the outlay involved in working up and, not
least, regarding safety aspects, which prevent conversion on a commercial
scale.
More particularly, an object of the present invention is, especially, to
meet the following requirements of the process:
a.) Use of a catalyst system consisting of inexpensive materials which are
freely available on the market and which generate the active catalyst
species in situ under the given reaction conditions, in contrast to the
catalysts described hitherto, which in some cases must be prepared in
separate process steps before the actual oxidation reaction or are used up
during the reaction.
b.) Use of a catalyst system which is highly active and at the same time
has a long life and which, after the reaction, can be recycled and used
again repeatedly without special measures having to be taken.
c.) Use of a reaction system consisting of different phases which are
immiscible at room temperature, one phase containing the catalyst in
dissolved or suspended form and a further phase containing the substrate
and product formed during the reaction in dissolved form, which allows the
substrate/product phase on the one hand and the catalyst phase on the
other hand to be separated after the reaction and accordingly enables the
product to be isolated in a simple manner and in a high yield and allows
the catalyst phase to be recycled at low cost.
SUMMARY OF THE INVENTION
The above and other objects of the invention can be achieved by converting
trimethylphenol by oxidation with oxygen or an oxygen-containing gas
mixture in the presence of a catalyst containing at least a copper halide
in a two-phase reaction medium at elevated temperature.
A feature of the process is that the reaction is carried out in the
reaction medium consisting of water and an aliphatic alcohol having from 5
to 10 carbon atoms or consisting of water and an aliphatic alcohol having
from 1 to 4 carbon atoms and an aromatic hydrocarbon, in the presence of a
catalyst system consisting of a copper halide and additionally a
transition metal halide selected from the group consisting of iron,
chromium, manganese, cobalt, nickel, zinc and a halide of a rare earth
element, at temperatures of from 20 to 120.degree. C.
The reaction may be so carried out that the organic phase containing the
trimethylphenol substrate and consisting of a suitable solvent that is not
or only slightly water-soluble at room temperature is brought into contact
with the aqueous phase containing the catalyst system, and the reaction
mixture so prepared is brought into contact with an oxygen-containing gas
and, when the reaction is complete, the organic product phase is separated
from the aqueous, still active catalyst phase in order to isolate the
2,3,5-trimethyl-p-benzoquinone product.
That result was unexpected because, in aqueous systems of copper halides
and transition metal halides or halides of rare earth elements, the
formation of sparingly soluble, in some cases oligomeric or polymeric
hydrolysis products, which exhibit no selective catalytic action for the
studied oxidation, must be reckoned with.
DETAILED DESCRIPTION OF INVENITON
It has been found in the case of the present invention that, if a binary
catalyst system consisting of copper halides on the one hand and
transition metal halides or halides of elements from the group of the rare
earths on the other hand is used, no or only negligible deactivation of
the catalyst occurs, even when the aqueous catalyst phase is used
repeatedly, and the oxidation to 2,3,5-trimethyl-p-benzoquinone may be
carried out under the novel conditions in a manner that is both economical
and advantageous from a commercial point of view.
Yields of 2,3,5-trimethyl-p-benzoquinone of over 90% can be achieved even
when the catalyst phase is used repeatedly. The use of selected transition
metal halides, such as, for example, CrCl.sub.3, FeCl.sub.3 or ZnCl.sub.2,
offers a further economical advantage as compared, for example, with the
use of expensive LiCl.
The oxidizing agent used in the process according to the invention is
oxygen in pure form or in dilute form, for example air. Based on 1 liter
of reaction mixture, from 10 to 150 NL of gaseous oxygen are generally
supplied per hour. There may be mentioned as copper salts that are
suitable within the scope of the invention, without laying any claim to
completeness, substantially CuCl.sub.2 and CuBr.sub.2 or corresponding
Cu(I) salts such as CuCl or CuBr, especially CuCl.sub.2 and CuCl.
Preference is given to the use of Cu(II) chloride.
There may be mentioned as transition metal halides that are suitable within
the scope of the invention substantially chlorides of the transition
metals. Especially suitable are the halides of the elements of the fourth
period, such as, for example, halides of the elements Cr, Mn, Fe, Co, Ni
and Zn, as well as Ce from the group of the rare earths.
There are suitable as the reaction medium in admixture with water
especially branched and unbranched aliphatic C.sub.5 -C.sub.10, alcohols,
such as 1-pentanol, 1-hexanol, 1-heptanol, 1-octanol, 1-nonanol,
1-decanol, 2-ethylhexanol or cyclohexanol.
Also suitable as the reaction medium in admixture with water and an
aromatic hydrocarbon are branched and unbranched aliphatic alcohols, such
as methanol, ethanol, n-propanol, isopropanol, 1-butanol, 2-butanol and
tert.-butanol.
The aromatic hydrocarbons used are preferably those having from 6 to 8
carbon atoms, especially benzene, toluene, xylenes, or halo-substituted
aromatic compounds, such as chlorobenzene.
The aqueous catalyst phase is prepared by simply mixing the aqueous
solutions of the individual components or by dissolving the solid salt
compounds in water, which makes the process markedly simpler to carry out.
The molar ratio of copper halide to trimethylphenol may be varied within
wide ranges and is usually copper salt/trimethylphenol=from 0.1 to 10,
preferably from 0.2 to 3.
The transition metal halides may be used in a 0.1- to 10-fold amount, based
on trimethylphenol, preference is given to a 0.2- to 5-fold molar amount.
In the case of the use of copper(II) salts, the concentration of the
copper halide in the aqueous catalyst phase may be varied from 1 to 70 wt.
%, concentrations of from 5 to 30 wt. % are preferably used, the
transition metal halides or the rare earth halides are preferably used in
a concentration range of from 5 to 80 wt. %.
There may be used as additional activators for the reactions the systems
known from the prior art, copper salts such as copper(I) chloride or the
corresponding hydroxide are most advantageously used.
Two-phase mixtures which result, for example, from the use of water and a
solvent that is immiscible or miscible to only a limited extent with
water, are optionally provided with a phase-transfer catalyst. There come
into consideration as phase-transfer catalysts the conventional products
known per se, such as tetraalkylammonium halides, benzyltrialkylammonium
halides or hydrogen sulfates as well as the corresponding phosphonium
salts and also compounds from the group of the polyethylene glycols. The
novel process is generally carried out at normal pressure and at a
temperature of from 20 to 120.degree. C. The process may likewise be
carried out under pressure; operation under pressure is appropriate
especially in the case of oxygen-containing gas mixtures. The procedure
may be carried out both continuously and discontinuously.
In order to carry out the reaction, trimethylphenol is dissolved in the
organic component of the solvent system and added in metered amounts to
the aqueous phase containing the catalyst. In a different embodiment, a
portion of the organic solvent is placed in a vessel with the aqueous
phase before the start of the reaction, and the trimethylphenol solution
is added in metered amounts. In yet another variant of the reaction
procedure, the reaction is carried out batchwise, all the components being
placed in a vessel, with stirring, and the metered addition of the
oxygen-containing gas then being begun.
The concentration of trimethylphenol in the organic phase may be varied
within wide concentration ranges, the trimethyl-phenol concentration is
generally adjusted to from 5 to 80%, preferably from 10 to 50%.
The ratio by volume of water to organic solvent may vary within a range of
from 10:1 to 1:10, a range of from 3:1 to 1:5 is preferred.
The reaction temperature may be varied over a wide temperature interval,
the reaction is preferably carried out at from 20 to 1200.degree. C., in
an especially preferred embodiment the procedure is carried out at from 40
to 900.degree. C.
The 2,3,5-trimethyl-p-benzoquinone reaction product may be isolated in the
conventional manner, for example by means of vacuum and steam
distillation.
The process according to the invention is simple to carry out and supplies
the reaction product in a good yield and a high purity.
The yields were determined on a HP 5890 or HP 6890 gas chromatograph using
a J&W DB-5 capillary column having a length of 30 m, an inside diameter of
0.32 mm and a film thickness of 1 .mu.m. Tetradecane was used as the
internal standard. The reference substance used was TMQ, which was
purified by distillation and repeated crystallisation.
HPLC measurements were carried out on a system from Jasco, consisting of a
UV 975 UV detector, a PU 980 pump and an AS 950 automatic sampler. The
column used was an Intersil-ODS 3V-5.mu.250.times.4.6 mm inside diameter
from GL Sciences Inc. The above-described TMQ reference substance was used
as the external standard.
The Examples which follow are intended to explain the invention in greater
detail.
TMP stands for trimethylphenol.
TMQ stands for 2,3,5-trimethyl-p-benzoquinone.
EXAMPLES
Example 1
2.98 g of FeCl.sub.3 (18.4 mmol) and 0.91 g (9.2 mmol) of CuCl were
dissolved in water in a 100 ml three-necked flask (molar ratio
CuCl:FeCl.sub.3 =0.5). The catalyst concentration of the binary salt
mixture was 13.5 wt. % in the aqueous phase. A solution of 2.5 g of TMP
(=18.4 mmol) in 25 ml of hexanol was added to the aqueous catalyst phase
with vigorous stirring. The TMP concentration in the organic phase was 11
wt. %. The reaction mixture was heated to 60.degree. C., while gassing
with oxygen over a frit, and the progress of the reaction was monitored by
means of gas chromatography. When the reaction was complete, a TMQ yield
of 82.2% was obtained.
Examples 2 to 6
Analogously to Example 1, the components were placed in a 100 ml
three-necked flask, the TMP:CuCl.sub.2 :FeCl.sub.3 ratio being 1:0.75:1.5.
The concentration of the binary catalyst in the aqueous phase was 39.4 wt.
% in all the tests. The TMP-alcohol solution was added to the catalyst
phase used initially, the mixture was then brought to the indicated
temperature, and gassing with oxygen was begun. By varying the reaction
temperatures and the reaction times, the following results were obtained
at the end of the reaction.
TABLE 1
TMP conc. TMQ yield
Catalyst Stoichiometry Temp. H.sub.2
O/solvent in the solvent Time (GC % by
Example Alcohol (molar amount) TMP/CuCl.sub.2 /FeCl.sub.3 (.degree.
C.) wt./wt. (wt. %) (h) surface area)
2 1-hexanol CUCl.sub.2 (0.066) 1:0.75:1.5 70 1:0.79
24.6 1 97.7
FeCl.sub.3 (0.132)
3 1-octanol CuCl.sub.2 (0.066) 1:0.75:1.5 70 1:0.80
24.2 1 87.8
FeCl.sub.3 (0.132)
4 1-hexanol CuCl.sub.2 (0.066) 1:0.75:1.5 40 I:0.79
24.6 4 91.2
FeCl.sub.3 (0.132)
5 1-hexanol CUCl.sub.2 (0.066) 1:0.75:1.5 60 1:0.79
24.6 2 93.4
FeCl.sub.3 (0.132)
6 1-hexanol CuCl.sub.2 (0.066) 1:0.75:1.5 80 1:0.79
24.6 1 93.9
FeCl.sub.3 (0.132)
Examples 7 to 12
Copper(II) chloride and a transition metal chloride or a chloride of a rare
earth element were placed in the form of an aqueous solution in a glass
reactor in the amounts indicated in Table 2; 40 ml of 1-hexanol were added
and the mixture was heated to 65.degree. C. A solution of 12 g of
2,3,6-trimethylphenol (88 mmol) in 20 ml of 1-hexanol was then added
dropwise in the course of 3 hours, with stirring (900 rpm) and while
gassing with oxygen over a frit. When the addition was complete, stirring
was continued for a further 2 hours at 80.degree. C., while gassing with
oxygen, and the progress of the reaction was monitored by HPLC. When the
reaction was complete, the phases were separated, the organic phase was
washed twice with water, and the TMQ yield was determined by gas
chromatography using an internal standard.
TABLE 2
Catalyst conc. in
Catalyst the aqueous phase Stoichiometry H.sub.2
O/solvent TMQ yield
(molar amount [mmol]) (wt. %) TMP/CuCl.sub.2 /add.
wt./wt. (%)
Example 7 CuCl.sub.2 (0.066) 39.0 1:0.75:1.5 1:1.05
94.3
CrCl.sub.3 (0.132)
Example 8 CuCl.sub.2 (0.066) 40.9 1:0.75:1.5 1:1.33
93.7
MnCl.sub.2 (0.132)
Example 9 CuCl.sub.2 (0.066) 35.8 1:0.75:1.5 1:1.05
91.1
CoCl.sub.2 (0.132)
Example 10 CuCl.sub.2 (0.066) 38.4 1:0.75:1.5 1:1.18
93.0
NiCl.sub.2 (0.132)
Example 11 CuCl.sub.2 (0.066) 50.7 1:0.75:0.75 1:2.82
89.9
ZnCl.sub.2 (0.066)
Example 12 CuCl.sub.2 (0.066) 45.8 1:0.75:1.5 1:1.00
91.5
CeCl.sub.3 (0.132)
Example 13
Copper(II) chloride (66 mmol) and chromium(III) chloride (132 mmol) were
placed in the form of an aqueous solution in a glass reactor (catalyst
concentration in the aqueous phase: 39.0 wt. %); 40 ml of 1-hexanol were
added and the mixture was heated to 65.degree. C. A solution of 12 g of
2,3,6-trimethylphenol (88 mmol) in 20 ml of 1-hexanol was then added
dropwise in the course of 3 hours, with stirring (900 rpm) and while
gassing with oxygen over a frit. When the addition was complete, stirring
was continued for a further 2 hours at 80.degree. C., while gassing with
oxygen, and the progress of the reaction was monitored by HPLC. When the
reaction was complete, the phases were separated, the organic phase was
washed twice with water, and the TMQ yield was determined by gas
chromatography using an internal standard. The combined aqueous phases
were concentrated to the original volume in a rotary evaporator and
transferred to the glass reactor again as the catalyst solution. The
process was repeated several times.
TABLE 3
Example 13, Number of repetitions of TMQ yield
run the process (%)
1 1 92.0
2 2 94.2
3 3 94.3
4 4 93.8*
5 5 93.7
6 6 92.3
7 7 94.3
*HPLC analysis using an external standard
Examples 14 to 17
Copper(II) chloride (66 mmol) and chromium(III) chloride (132 mmol) were
placed in the form of an aqueous solution in a glass reactor (catalyst
concentration in the aqueous phase: 39.0 wt. %); the amount of the
respective alcohol indicated in Table 4 was added, and the mixture was
heated to the indicated temperature. A solution of 12 g of
2,3,6-trimethylphenol (88 mmol) in the amount of the respective alcohol
shown in Table 4 was then added dropwise in the course of 3 hours, with
stirring (900 rpm) and while gassing with oxygen over a frit. When the
addition was complete, stirring was continued for the time shown in Table
4 at the indicated temperature, while gassing with oxygen, and the
progress of the reaction was monitored by HPLC. When the reaction was
complete, the phases were separated, the organic phase was washed twice
with water, and the TMQ yield was determined by HPLC using an external
standard.
Further variations and modifications will be apparent to those skilled in
the art from the foregoing and are intended to be encompassed by the
claims appended hereto.
German priority application 199 49795.8 is relied on and incorporated
herein by reference.
TABLE 4
Amount of Amount of Temperature during
alcohol used alcohol for the dropwise
Temperature during Subsequent
initially the TMP addition subsequent
stirring stirring time TMQ yield
Alcohol (ml) solution (ml) (.degree. C.)
(.degree. C.) (h) (%)
Example 14 1-heptanol 40 20 65 80
2 93.6
Example 15 1-heptanol 40 20 70 70
5 93.3
Example 16 1-octanol 30 30 65 80
2 92.7
Example 17 1-octanol 30 30 75 75
4 94.7
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